Physical quantities can be measured and have a numerical magnitude and unit. There are two types of physical quantities: base quantities like length, mass, and time, and derived quantities like area and volume which are expressed in terms of base quantities. The International System of Units (SI) provides standardized base and derived units for measuring physical quantities. SI units use prefixes to denote multiples and submultiples of units, and scientific notation is commonly used to write very large or small numbers in a standardized form.

1. PHYSICAL QUANTITIES
• A physical quantity is quantity which can be
measured.
For Example: length, mass, time, temperature, electric
current, light intensity, volume and many others.
• A physical quantity is always measured of natural
non-living objects.
• Physical quantities have numerical magnitude and
unit.
For Example: If the length of a student is 104cm, then
104 is its numerical magnitude and cm is the unit of
measurement.

2. PHYSICAL QUANTITIES
• The another example of physical quantity is that when
a grocer says that each sugar bag contains 5 kg, he is
describing its numerical magnitude as well as the unit
of measurement. It would be meaningless to state 5 or
kg only.
• Physical quantities are of two types:
1. BASE QUANTITIES
2. DERIVED QUANTITIES

3. BASE QUANTITIES
• Base quantities are the quantities on the basis of
which other quantities are expressed.
• There are seven base quantities which include
length, mass, time, temperature, intensity of
light and amount of a substance.

4. DERIVED QUANTITIES
• Derived quantities are the quantities which are
expressed in terms of base quantities.
• These include area, volume, speed, force, work,
energy, power, electric charge.

5. SI UNITS
• SI Units- International System of Units
•What is unit?
Once a standard is set for quantity then it can be
expressed in terms of that standard quantity. This
standard quantity is called a unit.
• The eleventh General Conference on Weight and
Measures held in Paris in 1960 adopted a world-wide
system of measurements called International System
of Units. The International System of Units is referred
as SI.

6. BASE UNITS AND DERIVED UNITS
• The SI unit contains base units and derived units.
 BASE UNITS: The units that describe base quantities
are called base units.

7. BASE UNITS AND DERIVED UNITS
DERIVED UNITS:
Derived units are the units used to measure derived
quantities.

8. SI PREFIXES
• Prefixes are the words or letters which we add to the
beginning of a word to make a new word.
• For example, the word ‘’unhappy” consists of the
prefix “un” (which means not) combined with the
stem word “unhappy” means “not happy”.
• SI units have advantage that their multiples and sub-
multiples can be expressed in terms of prefixes.

9. TABLE OF PREFIXES

10. SI PREFIXES
• Note that the kilogram is the only SI unit with
a prefix as part of its name and symbol.
Because multiple prefixes may not be used, in
the case of the kilogram the prefix names are
used with the unit name "gram" and the prefix
symbols are used with the unit symbol "g."
With this exception, any SI prefix may be used
with any SI unit, including the degree Celsius
and its symbol °C.

11. SI PREFIXES
MULTIPLES AND SUB-MULTIPLES OF LENGHT

12. SCIENTIFIC NOTATION
• Scientific notation is a way to write large or small
numbers with some power of ten.
• Scientific notation has a number of useful properties
and is commonly used in calculators, by scientists,
mathematicians and engineers.
• For example, a number 62750 can be expressed as
62.758*103 or 6.275*104 or 0.6275*105. All these are
correct but the number that has one non-zero digit
before the decimal e.g.6.275*104 preferable be taken
as a standard form. Similarly the standard form of
0.00045 s is 4.5*10-4 s.

13. PRESENTATION BY:
HOORIA SHAHZAD
STUDENT AT:
BEACONHOUSE